At impact of a liquid drop on solid surface, an air bubble can be entrapped. Here, we show that two competing effects minimize the (relative) size this entrained bubble: for large velocity and droplets, inertia flattens bubble, whereas small capillary forces bubble. However, demonstrate experimentally, theoretically, numerically in between there is optimum, leading to maximal entrapment. For 1.8 mm diameter ethanol droplet, optimum achieved at 0.25 m/s. Our results have strong bearing...

Very fine sand is prepared in a well-defined and fully decompactified state by letting gas bubble through it. After turning off the stream, steel ball dropped on sand. On impact of ball, blown away all directions ("splash") an crater forms. When this cavity collapses, granular jet emerges driven straight into air. A second goes downwards air entrained during process, thus pushing surface material deep ground. The rises slowly towards surface, causing eruption. In addition to experiments...

A shallow, vertically shaken granular bed in a quasi 2-D container is studied experimentally yielding wider variety of phenomena than any previous study: (1) bouncing bed, (2) undulations, (3) Leidenfrost effect, (4) convection rolls, and (5) gas. These the transitions between them are characterized by dimensionless control parameters combined full experimental phase diagram.

Combining a laser pulse with liquid in microcapillary tubes series of experiments, fluid-mechanics group at University Twente finds new way generating highly focused and ultrafast jets understands how to control the jet speed.

This paper presents a first step in the field of probabilistic forecasting co-located wind and photovoltaic (PV) parks. The effect aggregation is analyzed with respect to forecast accuracy value at park Sweden using roughly three years data. We use fixed modelling framework where we post-process numerical weather predictions calibrated production forecasts, which prerequisite when placing optimal bids day-ahead market. results show that improves terms continuous ranked probability score,...

Granular material is vertically vibrated in a 2D container: above critical shaking strength, and for sufficient number of beads, crystalline cluster elevated supported by dilute gaseous layer fast beads underneath. We call this phenomenon the granular Leidenfrost effect. The experimental observations are explained hydrodynamic model featuring three dimensionless control parameters: energy input $S$, particle layers $F$, inelasticity collisions $\ensuremath{\epsilon}$. $(S,F)$ phase diagram,...

Self-similarity has been the paradigmatic picture for pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that inverse problem, an air bubble in water, is not self-similar strict sense: A disk quickly pulled water surface, leading to giant, cylindrical void which after collapse creates upward downward jet. Only limiting case large Froude number neck radius $h$ scales as $h(-\log h)^{1/4} \propto \tau^{1/2}$, purely inertial scaling. For any...

A circular disc hitting a water surface creates an impact crater which after collapse leads to vigorous jet. Upon axisymmetric air cavity forms and eventually pinches off in single point halfway down the cavity. Two fast sharp-pointed jets are observed shooting up- downwards from closure location, by then has turned into stagnation surrounded locally hyperbolic flow pattern. This flow, however, is not mechanism feeding jets. Using high-speed imaging numerical simulations we show that jetting...

In this paper we study the transient surface cavity which is created by controlled impact of a disk radius h0 on water at Froude numbers below 200. The dynamics free recorded high speed imaging and compared to boundary integral simulations. An excellent agreement found between both. flow surrounding measured with particle image velocimetry also agree perfectly field obtained from We present simple model for radial based collapse an infinite cylinder. This accounts observed asymmetry...

The impact of an object on a granular solid is ubiquitous phenomenon in nature, the scale which ranges from raindrop onto sand all way to that large asteroid planet. Despite obvious relevance these events, study underlying physics mechanisms guide them relatively young, with most work concentrated past decade. Upon impact, starts interact bed and experiences drag force sand. This ultimately leads phenomena such as crater formation creation transient cavity upon collapse may cause jet appear...

When deposited on a hot bath, volatile drops are observed to stay in levitation: the so-called Leidenfrost effect. Here, we discuss drop dynamics an inverse situation where room-temperature liquid nitrogen pool, and levitate vapor film generated by evaporation of bath. In seconds following deposition, observe that droplets start glide bath along straight path, only disrupted elastic bouncing close edges container. Initially at rest, these self-propelled accelerate within few reach velocities...

Under slightly supersaturated conditions, bubbles need many minutes to grow due the low gas diffusivity in liquids. When coalescence occurs, fact that have diffusively grown on top of a surface allows for control with precision location and timing at which takes place. Numerous coalescences two $\text{CO}_{2}$ microbubbles water are recorded frame rate ${\sim}65\,000~\text{fps}$ . The evolution coalescing process is analysed detail, differentiating among three phases: neck formation, wave...

Abstract We study experimentally the growth of an isolated gas bubble in a slightly supersaturated water–CO 2 solution at 6 atm pressure. In contrast to what was found previous experiments higher supersaturation, time evolution radius differs noticeably from existing theoretical solutions. trace differences back several combined effects concentration boundary layer around bubble, which we disentangle this work. early phase, interaction with surface on grows slows down process. contrast,...

Nanobubble nucleation is a problem that affects efficiency in electrocatalytic reactions since those bubbles can block the surface of catalytic sites. In this article, we focus on rate O2 nanobubbles resulting from electrooxidation H2O2 at Pt disk nanoelectrodes. Bubbles form almost instantaneously when critical peak current, inbp, applied, but for lower currents, bubble stochastic process which (induction) time, tind, dramatically decreases as applied current approaches consequence local...

Granular material is vibro-fluidized in N = 2 and 3 connected compartments, respectively. For sufficiently strong shaking the granular gas equi-partitioned, but if intensity lowered, clusters one compartment. The phase transition towards clustered state of 2nd order for 1st 3. In particular, latter hysteretic. experimental findings are accounted within a dynamical model that has exactly above properties.

We construct a ratchet of the Smoluchowski-Feynman type, consisting four vanes that are allowed to rotate freely in vibrofluidized granular gas. The necessary out-of-equilibrium environment is provided by inelastically colliding grains, and equally crucial symmetry breaking applying soft coating one side each vane. onset effect occurs at critical shaking strength via smooth, continuous phase transition. For very strong interact actively with gas convection roll develops, sustaining rotation vanes.

A solid object impacting on liquid creates a jet due to the collapse of impact cavity. Using visualization experiments with smoke particles and multiscale simulations we show that in addition high-speed air-jet is pushed out Despite an velocity only 1 m/s, this attains \emph{supersonic} speeds already when cavity slightly larger than mm diameter. The structure air flow resembles closely compressible through nozzle -- key difference here "nozzle" \emph{liquid} shrinking rapidly time.

Strongly vertically shaken granular matter can display a density inversion: A high-density cluster of beads is elevated by dilute gaslike layer fast underneath ("granular Leidenfrost effect"). For even stronger shaking the state becomes unstable and convection rolls emerge. This transition resembles classical onset in fluid heated from below at some critical Rayleigh number. The same seen molecular dynamics (MD) simulations material. strength for be calculated linear stability analysis...

We have designed and constructed an experimental system to study gas bubble growth in slightly supersaturated liquids. This is achieved by working with carbon dioxide dissolved water, pressurized at a maximum of \documentclass[12pt]{minimal}\begin{document}$\mathrm{1\;\mathrm{M}\mathrm{Pa}}$\end{document}1M Pa applying small pressure drop from saturation conditions. Bubbles grow hydrophobic cavities etched on silicon wafers, which allows us control their number position. Hence, the...

Control over the bubble growth rates forming on electrodes of water-splitting cells or chemical reactors is critical with respect to attainment higher energy efficiencies within these devices. This study focuses diffusion-driven dynamics a succession H2 bubbles generated at flat silicon electrode substrate. Controlled nucleation achieved by means single site consisting hydrophobic micropit etched micrometer-sized pillar. In our experimental configuration constant-current electrolysis, we...

We investigate the spontaneous oscillations of drops levitated above an air cushion, eventually inducing a breaking axisymmetry and appearance `star drops'. This is strongly reminiscent Leidenfrost stars that are observed for floating hot substrate. The key advantage this work we inject airflow at constant rate below drop, thus eliminating thermal effects allowing better control flow rate. perform experiments with different viscosities observe stable states, chimney instabilities. find given...

Bubbles are known to hinder electrochemical processes in water-splitting electrodes. In this study, we present a novel method promote gas evolution away from the electrode surface. We consider ring microelectrode encircling hydrophobic microcavity which succession of bubbles grows. The microelectrode, tested under alkaline water electrolysis conditions, does not suffer bubble coverage. Consequently, chronopotentiometric fluctuations cell weaker than those associated with conventional...

The presence of bubbles in gas-evolving electrolytic processes can heavily alter the mass transport gaseous products and induce severe overpotential penalties at electrode through action bubble coverage (hyperpolarization) electrolyte constriction (Ohmic shielding). However, formation also alleviate by lowering concentration dissolved gas vicinity electrode. In this study, we investigate latter considering growth successive hydrogen driven a constant current alkaline-water electrolysis their...